NUM has released a sophisticated system-wide functional safety architecture for its CNC system, providing an exceptionally scalable solution that can be applied very easily to almost any type of machine tool – regardless of complexity or number of axes. Known as NUMSafe, it includes a dedicated safety PLC, safe input and output modules, and digital servo drives with built-in safe motion monitoring. It is compatible with NUM’s new-generation Flexium+ CNC platform.
According to NUM’s Chief Technical Officer, Massimiliano Menegotto, “Functional safety is becoming a mandatory requirement for most types of machine tool, independent of the machine’s performance, accuracy and complexity. As well as improving operator safety, it also increases machine productivity and availability”.
Integrated safety functionality
Until relatively recently, designers wishing to implement even basic functional safety schemes on CNC machines were forced to use electromechanical safety technology such as special contactors and relays. This approach involved significant extra component and wiring costs, as well as increased machine development and build times. By integrating safety functionality across the entire CNC platform NUMSafe minimizes the need for additional hardware and simplifies software development, to OEM’s considerable advantage. Furthermore, end users benefit from a strong increase in machine productivity because it is no longer necessary to power off the complete machine every time there is an element of human interaction; instead, protection can be ensured by dedicated functions which limit the movement, speed and position of axes.
To help machine builders minimize development time the application programs for the safety PLC are created using the same suite of powerful software tools that is used to commission the entire system, including the CNC, PLC, drives and I/O modules. The logic of the safety application is programmed using function blocks such as ‘E-Stop’, ‘Operation Mode’, ‘AND’, ‘OR, etc, linked to safe inputs and outputs.
A cost-saving benefit of NUM’s safety architecture is that there is no need for an additional encoder on machine axes that implement safety functions. Motor feedback can be derived from safe encoders which return position and redundant position data to the drive using a secure certified protocol, or, in the case of synchronous motors, any standard sin/cos encoder.